'SyntaxError' while unpacking dict in Python

Question

When I am trying to run an example of pychromecast library, I get the following failure:

~/pychromecast $ python example.py 
Traceback (most recent call last):
File "example.py", line 11, in <module>
import pychromecast.controllers.youtube as youtube
File "/home/pi/pychromecast/pychromecast/controllers/youtube.py", line 27
REQUEST_PARAMS_SET_PLAYLIST = {**BASE_REQUEST_PARAMS, **SET_PLAYLIST_METHOD}
                                ^
SyntaxError: invalid syntax

I've tried running this in both Python2 and Python3. What is wrong here?

Link to offending line: github.com/ur1katz/pychromecast/blob/master/pychromecast/… — Irfan
– Irfan, Commented Feb 23, 2017 at 15:56
This means that the library only supports modern Python. {**BASE_REQUEST_PARAMS, **SET_PLAYLIST_METHOD} works in Python 3.5 and above. — vaultah
– vaultah, Commented Feb 23, 2017 at 15:58

Moinuddin Quadri · Accepted Answer · 2017-02-23 16:13:23Z

3

This syntax was released with Python 3.5 as the part of PEP 448 - Additional Unpacking Generalizations.

As per the document: since Python 3.5, tuple, list, set, and dictionary displays allow multiple unpackings like:

>>> *range(4), 4
(0, 1, 2, 3, 4)

>>> [*range(4), 4]
[0, 1, 2, 3, 4]

>>> {*range(4), 4, *(5, 6, 7)}
{0, 1, 2, 3, 4, 5, 6, 7}

>>> {'x': 1, **{'y': 2}}
{'x': 1, 'y': 2}

edited Feb 23, 2017 at 16:13

answered Feb 23, 2017 at 16:05

Moinuddin Quadri

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1 Comment

vaultah Over a year ago

{*..., *...} would create a set, but {**..., **...} creates a dictionary.

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